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Two types of ATP‐sensitive potassium channels in rat portal vein smooth muscle cells
Author(s) -
Zhang HL.,
Bolton T.B.
Publication year - 1996
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1996.tb15372.x
Subject(s) - pinacidil , glibenclamide , potassium channel , biophysics , chemistry , patch clamp , cromakalim , smooth muscle , conductance , nucleotide , anatomy , medicine , biochemistry , endocrinology , biology , physics , receptor , condensed matter physics , gene , diabetes mellitus
1 . Single‐channel recordings were made from single, enzymatically isolated smooth muscle cells of rat portal vein by the patch‐clamp technique. 2 . Unitary potassium currents were identified through two types of K‐channels with conductances in 60:130 mM K‐gradient of 50 and 22 pS; these are referred to as LK and MK channels respectively. 3 . The LK channels became extremely active if isolated patches were created into nucleotide‐free solution; activity was inhibited by ATP applied to the inner surface of the patch with a half maximal inhibition (K i ) of 11–23 μ m . Channel activity declined and disappeared with time and could be regenerated by a brief application of Mg‐ATP or a nucleoside diphosphate such as UDP (in the presence of Mg). LK channel activity was rarely stimulated by levcromakalim and not by pinacidil (K‐channel openers, KCOs) but was blocked by glibenclamide. 4 . Activity of MK channels declined if isolated patches were created into nucleotide free solution; activity reappeared if UDP or ATP alone (in the presence of Mg) was applied; pinacidil or levcromakalim in the presence of ATP or UDP further increased channel activity which was blocked by glibenclamide. 5 . The LK channel inhibited by ATP i is very similar in its conductance and other properties to the K ATP channel described in tissues other than smooth muscle, in its conductance and properties the MK channel resembles the K NDP channel we have previous described as present in other smooth muscles and opening in responses to KCOs.